yC-MRLF 


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GIFT  OF 


i 


No.  1957 


DESCRIPTION 


OF 


TELESCOPIC  MUSKET  SIGHTS 

MODELS  OF  1908  AND  I9I3 


(FOUR  PLATES) 


DECEMBER  14,  1908 


REVISED  JULY  22,  1912/r     ^OFTHE^^ 
REVISED  NOVEMBER  X8,  ct^^  y  E  R  S 1 1^  y 

v  o  .         OF 


WASHINGTON 

GOVERNMENT  PRINTING  OFFICE 

1917 


No.  1957 


DESCRIPTION 

OF 

TELESCOPIC  MUSKET  SIGHTS 

MODELS  OF  1908  AND  I9I3 


{FOUR  PLATES) 


DECEMBER  14,  1908 
REVISED  JULY  22,  1912 
REVISED  NOVEMBER  18,  1915 


WASHINGTON 
GOVERNMENT  PRINTING  OFFICE 
1917      . 


Wab  Department,  . 
Office  of  the  Chief  of  Ordnance, 

Washington,  November  18,  1915, 
This  manual  is  published  for  the  information  and  government  of  the  Regular 
Army  and  Organized  Militia  of  the  United  States. 
By  order  of  the  Secretary  of  Wftr : 

William  Crozier, 
Brigadier  General,  Chief  of  Ordnance. 
104718—17  (3) 


363177 


Digitized  by  the  Internet  Archive 

in  2007  with  funding  from 

IVIicrosoft  Corporation 


http://www.archive.org/details/descriptionoftelOOunitrich 


DESCRIPTION  OF  TELESCOPIC  MUSKET  SIGHTS. 


MODEL  OF  1908. 

1.  Throughout  this  description  frequent  reference  is  made  b}^ 
number  to  the  photographic  Plate  I  and  to  the  sectional  drawing, 
Plate  II.  On  either  plate  a  given  number  refers  to  the  same  part  of 
the  instrument.  A  nomenclature  table,  arranged  in  sequence  of  the 
reference  numbers,  will  also  be  found  on  page  7. 

2.  The  telescopic  musket  sight  consists  of  three  essential  parts,  the 
telescope,  indicated  by  numbers  1-11  and  20-28,  Gl-62,  Plate  I.  the 
lever  (50-60),  on  which  the  telescope  is  mounted  by  a  vertical  axis; 
and  the  slide  (30-39).  to  which  the  lever  is  secured  b}^  a  horizontal 
axis,  while  graduated  dials  provide  means  for  turning  the  instrumei<t 
on  both  of  these  axes. 

THE  TF.LESCOPE. 

3.  In  the  telescope  body  (1)  (see  PL  II)  is  mounted  the  objective 
cell  (10)  for  the  objective  (9),  which  has  a  clear  aperture  of  ^f  inch, 
a  focal  length  of  7  inches,  and  gives,  with  the  eyepiece,  a  power  of  6 
diameters  and  a  field  of  4J°.  The  telescope  is  provided  with  Porro 
erecting  prisms  (21)  (21),  mounted  in  accurately  milled  recesses  in 
the  prism  holder  (20)  and  held  in  place  under  constant  pressure  by 
the  prism  cap  springs  (23)  of  the  prism  caps  (22)  (24),  the  caps  being 
fastened  by  the  prism  cap  screws  (25).  ^  The  telescope  has  a  reticule 
holder  (2)  into  which  is  spun  the  glass  reticule  (3),  on  which  are 
etched  vertical  and  horizontal  cross  lines  and  stadia  lines,  the  latter 
being  so  placed. that  they  span  the  height  (5  feet  8  inches)  of  an  aver- 
age man  standing  at  a  distance  of  1,000,  1^500^  and  2ft00  yards ^  re- 
spectively. The  telescope  has  an  eye-lens  holder  (5)  for  the  Steinheil 
triple  achromatic  eye  lens  (4).  The  holder  has  a  long  threaded  por- 
tion by  which  it  is  screwed  into  the  body  and  by  which  means  for 
focusing  is  secured.  The  eye-lens  holder  is  locked  in  position  by  the 
focusing  lock  nut  (8)  and  is  provided  with  an  eye  cap  of  soft  rubber 
( 6 ) ,  fastened  by  the  eye-cap  ferrule  ( 7 ) .  On  each  telescope  is  fastened, 
hy  means  of  table  screws  (28),  the  wind  and  range  table  (26)  and 
drift  table  ^27)  and  on  the  rear  face  is  fastened  a  range  table  {61) 
which  shows  the  ranges  corresponding  to  the  three  stadia  lines. 

(5) 


.^i^$He"^le>fer- (56^)' slipports  the  telescope  body  by  means  of  the 
adjusting  screw  (58).  This  screw  forms  a  vertical  axis  for  the 
telescope,  and  the  segmental  worm  gear  (A),  together  with  the  drift 
screw  (53)  and  its  graduated  drift  dial  (55) ,  provide  means  for  turn- 
ing the  telescope  on  this  axis  for  drift  and  wind  corrections. 

5.  The  slide  (30)  supports  the  lever  (50)  on  the  horizontal  axis  (C). 
The  pin  (D)  of  the  lever  engages  with  the  internal  hardened  steel  cam 
(E)  of  the  range  dial  (32),  and  is  kept  in  contact  with  it  by  the  lever 
spring  (31).  The  inner  circumference  of  the  range  dial  is  conical 
and  fits  in  a  conical  bearing,  so  that  it  can  be  clamped  in  any  desired 
position  by  tightening  the  range-dial  knob  (34)  against  the  keyed 
range-dial  washer  (33).  By  turning  the  dial  (32)  the  telescope  is 
rotated  on  the  horizontal  axis  (C) ,  giving  the  proper  depression  angle 
for  range  correction. 

The  telescopic  sight  hrachet  is  assemhled  to  the  receiver  of  the  rifle  hy 
means  of  screws.  The  sight  is  mounted  on  the  hracket  hy  means  of  the 
dovetail  (B)  in  the  slide  {30)  and  is  held  in  position  hy  means  of  the 
catch  {S6\  which  may  engage  in  either  of  the  two  notches  in  the  hracket. 
The  catch  can  be  released  by  pressing  the  catch  nut  (38). 

ADJUSTMENT   OF   THE    INSTRUMENT. 

For  focus. — In  adjusting  the  instrument  at  the  factory  the  reti- 
cule is  set  exactly  in  the  focal  plane  of  the  objective,  which  has  a 
universal  focus  beyond  100  feet,  and  the  eyepiece  is  set  for  the  vision 
of  an  average  observer.  Should  alteration  of  the  focus  of  the  eye- 
piece be  necessary  to  suit  special  conditions,  unscrew  the  focusing 
lock  nut  (8)  and  screw  the  eyepiece  out  or  in  until  the  cross  lines  of 
the  reticule  are  sharply  defined,  and  until  at  the  same  time  the  image 
of  the  target  is  clearly  visible.  Then  move  the  head  up  and  down, 
so  that  the  eye  may  travel  across  the  eyepiece.  If  the  focus  has  been 
correctly  found  there  will  be  no  parallax,  that  is,  no  apparent  motion 
of  the  cross  wires  with  reference  to  the  target  when  the  eye  moves 
across  the  field.  The  focus  being  accurately  adjusted,  be  sure  to 
lock  the  eye-lens  holder  by  tightening  the  focusing,  lock  nut  (8). 
The  rubber  eye  cap  can  now  be  turned,  without  affecting  the  focus, 
to  any  desired  position.  If  the  rubber  cap  does  not  turn  easily, 
loosen  the  eye-cap  ferrule  (f )  and  tighten  it  again  when  the  adjust- 
ment is  made. 

For  elevation. — The  range  dial  is  graduated  from  0  to  3,000  yards 
by  20-yard  divisions.  To  make  elevation  adjustment  attach  the 
telescopic  sight  to  the  bracket  of  the  rifle,  being  sure  that  both  the 
slide  and  the  bracket  are  perfectly  clean,  secure  the  rifle  in  a  fixed 
rest,  and  set  the  service  sight  of  the  rifle  at  500  yards.    Set  the  range 


dial  of  the  telesoopic  sight  at  the  same  range  and  clamp  it.  The  cross 
wires  of  the  telescopic  sight  and  the  line  of  sight  of  the  i^fie  through  the 
service  sight  should  then  bisect  the  target  exactly.  If  the  cross  wires 
of  the  telescopic  sight  are  too  high,  unscrew  the  hexagon  adjusting- 
screw  nut  (59 ) ,  using  the  screw  driver  provided  with  the  sights  and  turn 
the  adjusting  screw  (58)  clockwise,  which  will  cause  the  cross  wires 
to  drop  on  the  target.  Turning  the  adjusting  screw  in  the  opposite 
direction  will  make  the  cross  wires  rise.  After  the  adjustment  is 
made  be  sure  to  tighten  the  nut.  The  rifle  is  then  fired  several  shots 
to  test  elevation^  the  necessary  correction  being  made  by  the  Tnoverrient 
of  the  adjusting  screw  until  a  satisfactory  elevation  is  obtained. 

For  drift. — The  graduations  on  the  drift  dial  (55)  correspond  to 
1  inch  on  the  target  at  a  range  of  100  yards.  Turning  the  dial  clock- 
wise corrects  to  the  right,  as  indicated'by  the  letter  (R)  and  counter- 
clockwise to  the  left,  as  indicated  by  the  letter  (L).  There  are  38 
points  of  left  and  46  points  of  right  drift  correction.  The  drift  dial 
should  read  "  0  "  when  the  optical  axis  of  the  instrument  is  parallel 
with  the  bore  of  the  rifle.  Should  it  be  necessary  to  adjust  the  dial; 
secure  the  rifle  in  a  fixed  rest,  make  the  optical  axis  of  the  instrument 
parallel  with  the  line  of  sight  through  the  service  sight,  by  sighting  at 
some  distant  object,  loosen  the  two  drift-dial  screws  (57)  which  will 
permit  rotating  the  dial  without  moving  the  drift  screw,  set  the  dial 
exactly  at  "  0  "  and  clamp  the  screws  firmly  against. 


Nomenclature  table. 


1.  Body. 

32. 

Range  dial. 

2.  Reticule  holder. 

33. 

Range-dial  washer. 

3.  Reticule. 

34. 

Range-dial  knob. 

4.  Triple  eye  lens. 

35. 

Spring  cotter  (for  knob ) . 

5.  Triple  eye-lens  holder. 

36. 

Catch. 

6.  Eye  cap. 

37. 

Catch  spring. 

7.  Eye-cap  ferrule. 

38. 

Catch  nut. 

8.  Focusing  lock  nut. 

39. 

Range-dial  washer  pin. 

9.  Objective. 

50. 

Lever. 

10.  Objective  cell. 

51. 

Spanner  nuts. 

11.  Body  screws. 

-    52. 

Spring  cotters  (for  nuts) 

20.  Prism  holder. 

53. 

Drift  screw. 

21.  Prisms. 

54. 

Drift-screw  washer. 

22.  Prism  cap. 

55. 

Drift  dial. 

23.  Prism-cap  springs. 

56. 

Drift-dial  washer. 

24.  Prism  cap. 

57. 

Drift-dial  screws. 

25.  Prism-cap  screws. 

58. 

Adjusting  screw. 

26.  Wind  and  range  table. 

59. 

Adjusting-screw  nut. 

27.  Drift  table. 

60. 

Drift-dial  pin. 

28.  Table  screws. 

61. 

Range  table. 

30.  Slide. 

62. 

Range-table  screws. 

31.  Lever  spring. 

70. 

Screw  driver. 

POUCH. 

Model  of  1911  for  telescopic  musket  sights. 

The  pouch  furnished  for  the  telescopic  sight  is  made  of  russet  collar 
leather.  It  is  provid^ed  with  a  douhle  hook  and  a  leather  straj)^  so  that 
it  can  he  carried  either  on  the  cartridge  helt  or  over  the  shoulder. 

MODEL  OF  1913. 

The  telescopic  musket  sight,  model  of  1913,  is  shown  on  photo- 
graphic Plate  III.  A  sectional  drawing  of  the  instrument  is  shown 
on  Plate  IV.  A  nomenclature  table,  with  illustration  number,  piece 
mark,  and  drawing  number,  will  be  found  below.  The  illustration 
numbers  given  in  nomenclature  table  refer  to  Plates  III  and  IV. 

This  instrument  is  almost  identical  with  the  telescopic  musket 
sight,  model  of  1908,  and  differs  only  the  following  particulars : 

{a)  The  objective  (27)  is  held  in  the  objective  cell  (24)  by  the 
objective  retaining  ring  (25)  which  is  held  in- place  by  the  objective 
retaining  nut  (26). 

(b)  The  reticule  holder  (41)  is  held  in  the  telescope  body  (5)  by 
the  reticule-holder  nut  (42),  which  screws  into  the  telescope  body. 
The  reticule  is  prevented  from  turning  by  the  reticule-holder  lock 
screw  (43). 

{c)  The  triple  eye-lens  holder  (50)  has  a  short  threaded  portion 
by  which  it  is  screwed  into  the  telescope  body  (5)  and  by  means  of 
which  the  instrument  is  focused.  To  alter  the  focus,  remove  the 
focusing-lock  collar  cap  (21),  loosen  the  focusing-lock  collar  (19)  by 
unscrewing  the  focusing-lock  collar  screw  (20),  then  screw  the  triple 
eye-lens  holder  (50)  in  or  out  until  the  cross  lines  on  the  reticule  (40) 
are  sharply  defined  and  the  image  of  the  target  is  clearly  visible. 
After  the  focus  has  been  determined,  lock  the  triple  eye-lens  holder 
(50)  by  screwing  the  focusing-lock  collar  screw  (20)  into  the  telescope 
body  until  the  focusing-lock  collar  bears  tightly  enough  to  prevent 
turning,  then  replace  the  focusing-lock  collar  cap  (21).  The  rubber 
eye  cap  (18)  can  now  be  turned  without  affecting  the  focus  of  the 
instrument.  If  the  eye  cap  (18)  does  not  turn  easily,  loosen  the  eye- 
cap  ferrule  (17)  and  tighten  again  when  adjustment  is  made. 


Nomenclature. 

Illustra- 

Illustra- 

tion No. 

tion  No. 

1. 

Adjusting-screw  spanner  nut. 

28.  Prism  holder. 

2. 

Adjusting-screw  nut. 

29.  Prism-holder  screw. 

3. 

Adjusting  screw. 

30.  Prism  cap. 

4. 

Adjusting-screw  hole  cap  screw. 

31.  Prism-cap  spring. 

5. 

Body. 

32.  Prism-cap  screw. 

6. 

Catch  nut. 

33.  Prism. 

7. 

Catch  spring. 

34.  Range-dial  knob. 

8. 

Catch. 

35.  Range-dial  washer. 

9. 

Drift  table. 

36.  Range-dial  washer  pin. 

10. 

Drift-table  screws. 

37.  Range  table. 

11. 

Drift-dial  washer. 

38.  Range-table  screws. 

12. 

Drift-dial  washer  screw. 

39.  Range  dial. 

13. 

Drift  screw. 

40.  Reticule. 

14. 

Drift-screw  washer. 

41.  Reticule  holder. 

15. 

Drift  dial. 

42.  Reticule-holder  nut. 

16. 

Drift-dial  pin. 

43.  Reticule-holder  lock  screw. 

17. 

Eye-cap  ferrule. 

44.  Standard  split  pin. 

18. 

Eye  cap. 

45.  Slide. 

19. 

Focusing-lock  collar. 

46.  Screw  driver  wrench. 

20. 

Focusing-lock  collar  screw. 

47.  Spanner  nut. 

21. 

Focusing-lock  collar  cap. 

48.  Standard  split  pin. 

22. 

Lever. 

49.  Triple  eye-lens  holder  ferrule. 

23. 

Lever  spring. 

50.  Triple  eye-lens  holder. 

24. 

Objective  cell. 

51.  Triple  eye  lens. 

25. 

Objective-retaining  ring. 

52.  Wind  and  range  table. 

26. 

Objective-retaining  nut. 

53.  Wind  and  range  table  screws. 

27. 

Objective. 

CARE  AND  PRESERTATION. 

Telescopic  sights  are  necessarily  delicate  instruments  and  must 
not  be  subjected  to  rough  usage,  jars,  or  strains.  When  not  in  use 
the  telescope  should  be  kept  in  its  pouch  and  stored  in  a  dry  place. 
It  should  be  occasionally  examined  to  insure  its,  not  being  corroded, 
and  all  traces  of  dust  or  moisture  should  be  removed  before  being  put 
away.  To  obtain  satisfactory  vision  the  glasses  should  be  kept 
perfectly  clean  and  dry.  In  case  moisture  collects  on  the  glasses, 
place  the  telescope  in  a  gentle  warmth ;  this  is  usually  sufficient  to 
remove  it.  A  piece  of  chamois  skin  or  a  clean  linen  handkerchief 
will  answer  for  cleaning  purposes,  care  being  taken  that  the  cleaning 
material  does  not  contain  any  dirt  or  grit.  These  sights  before  issue 
are  carefully  adjusted  to  selected  rifles  and  their  adjustment  proven 
by  actual  firings.  The  prism  holder  should  never  be  opened  except 
by  a  competent  person.  The  body  of  this  telescope  and  its  objective 
must  remain  intact.  The  eyepiece  can  be /removed  after  loosening 
the  focusing  lock  nut  and  the  eyelens  and  reticule  then  cleaned. 
Before  incasing  the  prisms  at  the  factory  the  interior  of  the  body  is 


10 

thoroughly  cleaned  and  all  particles  removed.  If  any  fine  particles 
should  be  left  in  the  body  or  if  the  body  should  he  opened  and  particles 
enter,  they  wUl  settle  upon  the  reticule  and  when  magnified  by  the 
eye-lens  obscure  the  vision.  Small  holes  are  punched  through  the 
rubber  eye  cap  to  permit  the  escape  of  air  on  recoil,  thereby  prevent- 
ing suction  on  counter  recoil. 

Wab  Depaetment, 

Office  of  the  Chief  of  Oednance, 

Washington,  November  18,  1915. 
December  14,  1908. 
Revised  July  22,  1912. 
Revised  November  18,  1915. 
FoEM  No.  1957. 
Ed.  June  13-17—3,000. 
39275-702. 

O 


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